PICTURES: Earth Hour darkens world's landmarks

Portugal Earth Hour

Francisco Seco / AP

Young participants look at a performer wearing a luminous costume entertaining the crowd during the symbolic switching off of the lights known as Earth Hour, Saturday, March 28, 2015, in Lisbon, Portugal. At 8:30 p.m. local time, individuals, businesses, cities and landmarks around the world switched off their lights for one hour to focus attention on climate change.

Young participants look at a performer wearing a luminous costume entertaining the crowd during the symbolic switching off of the lights known as Earth Hour, Saturday, March 28, 2015, in Lisbon, Portugal. At 8:30 p.m. local time, individuals, businesses, cities and landmarks around the world switched off their lights for one hour to focus attention on climate change. (Francisco Seco / AP)

A boy with his face decorated with luminous ink poses for a photograph with others during the symbolic switching off of the lights known as Earth Hour, Saturday, March 28, 2015, in Lisbon, Portugal.

A boy with his face decorated with luminous ink poses for a photograph with others during the symbolic switching off of the lights known as Earth Hour, Saturday, March 28, 2015, in Lisbon, Portugal. (Francisco Seco / AP)